\(x^2-2\left(y-1\right)x+y^2-3=0\)
\(\Delta'=\left(y-1\right)^2-\left(y^2-3\right)\ge0\)
\(\Leftrightarrow4-2y\ge0\Rightarrow y\le2\)
\(\Rightarrow y_{max}=2\)
Khi đó \(x=\frac{2\left(y-1\right)}{2}=y-1=1\)
Vậy \(\left(x;y\right)=\left(1;2\right)\)